1. Field of the Invention
The present invention relates to a ball screw, and more particularly to a ball screw with a circulating assembly.
2. Description of the Prior Art
Referring to FIG. 1 showing a first conventional ball screw with a circulating element, the circulating element 11 is axially installed into an end surface of the nut 12 and includes a nail portion 111. The nail portion 111 protrudes from the circulating element 11 and into the outer helical groove 131 of the screw shaft 13 for connecting the outer helical groove 131 of the screw shaft 13 to the circulating element 11. The circulating element 11 can guide the balls 14 into the circulating hole (not shown) in the nut 12 to allow the balls 14 between the screw shaft 13 and the nut 12 to circulate endlessly and eliminate the impact caused by the circulation of the balls 14. However, since the outer helical groove 131 of the screw shaft 13 and the nail portion 111 of the circulating element 11 are fitted in a concave-convex manner, so that one end of the outer helical groove 131 of the screw shaft 13 must be open. In other words, the outer helical groove 131 of the screw shaft 13 must extend to the shoulder portion of the screw shaft 13, thus reducing the service life of the ball screw.
Referring to FIG. 2 showing a second conventional ball screw with circulating assembly, the circulating assembly is of the sectional type, namely it consists of an inner circulating block 16 and an outer circulating block 17 so that it can be applied to the screw shaft 18 whose helical groove doesn't extend to the shoulder portion thereof. However, since the top surface 171 and the bottom surface 172 of the outer circulating block 17 are both planar and parallel to each other without any angle therebetween, such a structure must cooperate with a nut 19 with a larger outer diameter and is thus not applicable to the nuts of special specifications, especially the nuts by European industrial standards, such as the nuts by Deutsche industry norm.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.